Compensation of baseline wander

ABSTRACT

A circuit for compensation of baseline voltage wander operating at an input of an isolator is disclosed. The circuit can compensate electronically the frequency response of an isolation circuit (e.g., a transformer) by increasing the pass band in the low frequency region in order to minimize the baseline wander caused by low inductance windings. The compensation circuit can be used to inject a current ramp proportional to the amplitude and the duration of the pulse and inversely proportional to the open circuit inductance of the isolation circuit.

CLAIM OF PRIORITY

This application claims the benefit of the priority of Spanish PatentApplication Number 201631006, titled “COMPENSATION OF BASELINE WANDER,”and filed with the Spanish Patent and Trademark Office (SPTMO) on Jul.22, 2016, the entirety of which is hereby incorporated by referenceherein.

BACKGROUND

Many communication systems exchange data using an isolator circuit, suchas a transformer. For example, in an Ethernet communication system, theIEEE 802.3 (e.g., Institute of Electrical and Electronics Engineers802.3-2012) standard specifies that electrical isolation be providedbetween an Ethernet physical layer circuit—usually referred to as an“Ethernet PHY”—and an Ethernet port (e.g., a medium-dependent interface(MDI)), which provides a physical and electrical connection to a cablingmedium (e.g., ANSI/TIA-568-C.0, Generic Telecommunications Cabling forCustomer Premises, Category 5)). In such Ethernet implementations, datamay be transmitted from an Ethernet-enabled device onto the cablingmedium using a transformer.

However, using a transformer to transmit data between isolated systemsor subsystems may be associated with certain drawbacks. For example,baseline wander may occur, when voltage driven on the transformer droopsover time as energy leaks out of the transformer due to its inductivenature in conjunction with other impedances to which it is coupled.Applications and standards may require limiting such baseline wander.

Prior approaches to limiting baseline wander include using a transformerhaving an inductance value that either complicates or precludes use ofan integrated transformer circuit. For example, some Ethernet standardsmay translate to use of a transformer inductance of at least 80microHenry (μH) or more, such as even 350 μH or more.

SUMMARY OF THE DISCLOSURE

Embodiments of the present disclosure can provide a circuit forcompensation of overall baseline voltage wander operating at an input ofan isolator. The circuit can include a filter circuit and a drivercircuit. The filter circuit can be configured to receive an inputvoltage signal from an input of the isolator and configured to generatea filtered representation of the voltage signal. The driver circuit canbe configured to use information about a voltage magnitude extractedfrom the filtered representation of the voltage signal to generate anoutput current ramp signal. The driver circuit can be further configuredto inject the output current ramp signal into the input of the isolatorto reduce or suppress voltage droop in the input voltage signal when theinput voltage signal is applied to the input of the isolator.

In an example, a compensation loop circuit for compensation of baselinevoltage wander at an input of an isolator can include a filter circuit,a gain circuit, and a driver circuit. The filter circuit can be coupledto an input of the isolator. The filter circuit can be configured toreceive an input voltage signal from the input of the isolator andgenerate a filtered representation of the voltage signal. The gaincircuit can be coupled to an output of the filter circuit, and can beconfigured to amplify the filtered representation of the voltage signalto generate an amplified voltage signal. The driver circuit can becoupled to an output of the gain circuit and an input of the filtercircuit to form the compensation loop circuit. The driver circuit can beconfigured to generate an output current ramp signal based on theamplified voltage signal. The driver circuit can be further configuredto inject the output current ramp signal into the input of the isolatorto reduce or suppress voltage droop in the input voltage signal when theinput voltage signal is applied to the input of the isolator. The outputcurrent ramp signal can be configurable based on a voltage gainassociated with the input voltage signal and an output voltage signalcorresponding to the output current ramp signal.

In an example, a method for generating a signal to compensate baselinevoltage wander can include receiving an input voltage signal from aninput of an isolator circuit. The received input voltage signal can befiltered to generate a filtered representation of the voltage signal. Acurrent ramp signal can be generated, where the current ramp signal canbe proportional to inductance associated with the isolator circuit and avoltage magnitude extracted from the filtered representation of thevoltage signal. The current ramp signal can be injected into the inputof the isolator to reduce or suppress voltage droop in the input voltagesignal when the input voltage signal is applied to the input of theisolator.

This overview is intended to provide an overview of subject matter ofthe present patent application. It is not intended to provide anexclusive or exhaustive explanation of the invention. The detaileddescription is included to provide further information about the presentpatent application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a communication system providing improved communicationof data using an isolator, in accordance with an example embodiment.

FIG. 2 depicts a communication circuit with an integrated compensationcircuit, in accordance with an example embodiment.

FIG. 3 illustrates a compensation circuit coupled to an equivalentcircuit representing a primary side of a transformer, in accordance withan example embodiment.

FIG. 4, FIG. 5 and FIG. 6 are signal diagrams depicting example signalsof the communication circuit, including the compensation circuit and theequivalent circuit, in accordance with an example embodiment.

FIG. 7 illustrates a compensation circuit, in accordance with an exampleembodiment.

FIG. 8 illustrates an example embodiment of a filter stage and a gainstage for the compensation circuit of FIG. 7.

FIG. 9A and FIG. 9B illustrate example embodiments of a compensationcircuit.

FIG. 10 illustrates a flow diagram of an example method for generating asignal to compensate baseline voltage wander, in accordance with anembodiment.

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

DETAILED DESCRIPTION

One approach can provide a compensation circuit to compensateelectronically the frequency response of an isolation circuit (e.g., atransformer) by increasing the pass band in the low frequency region inorder to minimize the baseline wander (e.g., voltage droop) caused bylow inductance windings. For example, the compensation circuit can beused to inject a current ramp proportional to the amplitude and theduration of the pulse and inversely proportional to the open circuitinductance (OCL) of the isolation circuit. This approach allows use ofan isolation circuit, such as a magnetic device, having a smallerinductance value than a corresponding isolation scheme lacking thecompensation circuit.

FIG. 1 depicts a communication system providing improved communicationof data using an isolator, in accordance with an example embodiment.Referring to FIG. 1, the communication system may include acommunication circuit 104 located on a first side of an isolationbarrier 107, a cable device 108 located on a second side of theisolation barrier, and an isolator circuit 106. The communicationcircuit 104 can be configured to receive a data signal 102 fortransmission across a cable via the isolator circuit 106. The cabledevice 108 can provide a data output signal 110 as a result of receivinga transmission from the communication circuit 104 over the isolatorcircuit 106.

The isolator circuit 106 can be configured to provide communicationbetween the communication circuit 104 and the cable device 108 acrossthe isolation barrier 107. In embodiments, the isolator circuit 106 canbe a transformer. In other embodiments, the isolator circuit 106 can beanother type of an isolator device for which baseline wander or othersimilar phenomena may be a concern, such as one or more of another typeof inductive isolator, an optical isolator, or a capacitive a isolator,as illustrative examples. In an embodiment, the isolator circuit caninclude a series and/or parallel combination of inductive devices.

FIG. 2 depicts a communication circuit with an integrated compensationcircuit, in accordance with an example embodiment. Referring to FIG. 2,the communication circuit 200 can include a data input 204, data input,encode and timing circuit 210, a driver circuit 212, a compensationcircuit 208, and a control circuit 206. The driver circuit 212 can becoupled to an isolator circuit 214, such as a transformer or anothertype of isolation circuit. In an embodiment, the components of thecommunication circuit 200 can be integrated on the same integratedcircuit substrate. In an embodiment, the components of the communicationcircuit 200 can be included in the same circuit package. In anembodiment, the isolation circuit 214 (or one or more portions of it)can be integrated on the same integrated circuit substrate as thecommunication circuit 200. In an embodiment, the isolation circuit 214(or one or more portions of it) can be a separate circuit, integrated ona second integrated circuit substrate packaged together in the samepackage as an integrated circuit substrate including the communicationcircuit 200.

The data input, encode and timing circuit 210 can be configured toreceive an input data signal 204 for transmission across the isolatorcircuit 214 to a cable device. In response, the data input, encode andtiming circuit 210 can be configured to perform one or more of datasynchronization, framing, encoding, or other operations, and cangenerate a driver input signal representing the input data 204 fortransmission. The driver circuit 212 can be configured to receive thedriver input signal from the data input, encode and timing circuit 210.In response, the driver circuit 212 can drive a corresponding signal onthe isolation circuit 214 (e.g., the primary side of a transformer). Thecompensation circuit 208 can be configured to provide a current to theisolation circuit 214 (e.g., to the primary side of the transformer) tocompensate for baseline wander that may be experienced at thetransformer in conjunction with transmitting the data signal. Thecontrol circuit 206 can be configured to receive a clock signal 202 andcontrol one or more of the data input, encode and timing circuit 210,the compensation circuit 208, or the driver circuit 212.

FIG. 3 illustrates a compensation circuit coupled to an equivalentcircuit representing a primary side of a transformer, in accordance withan example embodiment. Referring to FIG. 3, the driver circuit 304 caninclude a voltage driver circuit 304 a and a termination impedance 304b. The current compensation circuit 302 can include a controlled currentsource 302 a. The equivalent primary circuit 306 can include aninductance 308 and a resistance 310 representing a termination impedance(e.g., termination impedance at a secondary side of a transformer,reflected back to the primary side of the transformer). For clarity ofillustration, other components of the driver circuit 304 and the currentcompensation circuit 302 are omitted in FIG. 3. For example, thecontrolled current source 302 a of the current compensation circuit 302can include suitable components to generate selected currents, such asone or more of a digital to analog converter, a timer, and transistors,and can be controlled using control signals received from a controlcircuit (e.g., 206 in FIG. 2).

FIG. 3 illustrates an open-loop arrangement of the compensation circuit302, which can be used to compensate for baseline wander in instanceswhen voltage and duration of a voltage signal generated by the drivercircuit 304 are known. For example, the open-loop arrangement of thecompensation circuit 302 can be used in circuits with knowncharacteristics of the transmit signal (e.g., 10/100Base-T communicationcircuits). The compensation circuit 302 can be configured to generate acurrent to compensate for the baseline wander experienced at theequivalent primary circuit 306. That is, the compensation circuit 302can be configured to inject a current into the primary side of atransformer (e.g., the equivalent primary circuit 306) in an amount thatcompensates for any energy lost due to the inductive nature of thetransformer. The relationship between inductance, voltage and currentmay be represented by the following equation:

${{V(t)} = {L\frac{{di}(t)}{dt}}},$

where v(t) is the voltage at the equivalent primary circuit 306, i(t) isthe current in the equivalent primary circuit 306, and L is theinductance in the equivalent primary circuit 306 of the primary side ofthe transformer. To eliminate baseline wander, the compensation circuitcan be configured to establish a constant or substantially constantv(t). As an illustration, to generate a constant v(t), a current i(t)may be determined as follows:

${{\int{{di}(t)}} = {\frac{V}{L}{\int{dt}}}},$

${i(t)} = {{\frac{V}{L}\lbrack {t - {t\; 0}} \rbrack} = {\frac{V}{L}\Delta\; T}}$

Therefore, the current for generating a constant (or substantiallyconstant voltage) may be a current ramp proportional to time, with aslope of V/L.

FIG. 4, FIG. 5, and FIG. 6 are signal diagrams depicting example signalsof the communication circuit, including the compensation circuit and theequivalent circuit, in accordance with an example embodiment.

FIG. 4 shows an example driver pulse 408 generated by the driver circuit(e.g., 304). The driver pulse 408 is characterized by a certainamplitude and can be substantially constant. The driver pulse 408 canexperience a voltage division as a result of the termination impedances(e.g., 310). As a result, a voltage appearing on the primary side of atransformer (e.g., at the equivalent primary circuit 306) can be lowered(e.g., halved). FIG. 4 also illustrates an example voltage signal 404appearing at the equivalent primary circuit 306 as a result of thedriver pulse without any compensation, such as without the compensationcircuit or with the compensation circuit disabled. As seen in FIG. 4,the voltage signal 404 droops over time.

FIG. 4 further illustrates an example voltage signal appearing at theequivalent primary circuit 306, with a compensation current provided bythe compensation circuit 302, to eliminate or substantially eliminatethe voltage droop. As seen in FIG. 4, the primary voltage signal 406 isconstant or substantially constant. FIG. 4 further illustrates anexample compensation current signal 402, which can be provided by thecompensation circuit 302 to compensate for the voltage drop in theprimary voltage signal 404. As seen in FIG. 4, the current signal 402 isin the form of a ramp signal, starting at the beginning of the driverpulse 408 and having a slope selected as discussed above to produce aconstant or substantially constant voltage signal 406.

In an example, the compensation circuit 302 can be configured to providea current that only partially compensates for baseline wander or otherphenomenon. For example, the compensation circuit 302 can be configuredto provide a ramp current with a slope less than that required to fullycompensate. This may enable avoidance of providing a non-zero averagecompensation current. Even though some amount of baseline wander may beexperienced, the extent of baseline wander may be acceptable.

FIG. 5 illustrates an example current signal 500 generated in thetransformer primary side (e.g., at the equivalent primary circuit 306)using a compensation current less than the amount required to fullycompensate for baseline wander. As seen in FIG. 5, the compensationcurrent may produce a zero average DC current at the equivalent primarycircuit 306, but also allowing for a certain amount of baseline wander.

In an example, the compensation current gain (slope) can be limited to,e.g., avoid saturating the transformer. For example, the compensationcurrent generated by the compensation circuit 302 can be released afterevery ramp period compensating for a data pulse. In this way, thecumulative compensation current and/or primary current over time (manysignal periods) does not rise continuously (e.g., as seen in FIG. 4).

FIG. 6 illustrates an example voltage pulse 602 and a current signal 604produced in the transformer primary side using a limited gain (slope)compensation current that is released after the end of the pulse. Asseen in FIG. 6, the compensation current signal 604 can compensateduring the data pulse but allow energy to be released by the transformeroutside of the data pulse.

FIG. 7 illustrates a compensation circuit, in accordance with an exampleembodiment. Referring to FIG. 7, the compensation circuit 720 caninclude a band-pass filter circuit 722, a gain circuit 724, and acurrent driver circuit 726. As seen in FIG. 7, the compensation circuit720 can be provided in a closed-loop configuration, with the input tothe filtering circuit 722 being coupled to the output of the drivercircuit 726 (e.g., at the node 704). The compensation circuit 720 can beconnected to the equivalent primary circuit 706, driven by anuncompensated (or insufficiently compensated) communication circuit 702.In an example, the circuit 702 can be a push/pull driver circuit. In anexample, the equivalent primary circuit 706 can represent a primary sideof a transformer, including an inductance 710 and a resistance 708representing a termination impedance (e.g., termination impedance at asecondary side of a transformer, reflected back to the primary side ofthe transformer).

In an example, the loop of the compensation circuit 720 can result in acurrent, such as, e.g., a ramp current or similar current as discussedabove, being provided to the primary to compensate for the uncompensatedor insufficiently compensated communication circuit.

In an example, the compensation circuit 720 can be a stand-alone circuitor it can be co-integrated with the driver circuit 702 and/or theequivalent primary circuit 706.

In an example, the compensation circuit 720 configured in closed-loopmode can be used for compensating baseline wander of an output signal,when characteristics of the output signal are not known (e.g., pulseduration and voltage level). For example, the closed-loop compensationcircuit 720 can be used in connection with a full-duplex Gigabit PHYcircuit operating in 1000Base-T mode. In this case, the compensationcircuit can automatically boost low frequencies to reduce baselinewander droop of any signal at the output node 704 of the driver circuit702. Example closed-loop modeling of a compensation circuit isillustrated in connection with FIG. 9A and FIG. 9B.

Referring again to FIG. 2, the depicted communication circuit 200 can beconfigured to provide either single-ended or differential signals. Forexample, a driver circuit and a compensation circuit (such as circuits302, 304, 720, and 702 depicted in FIGS. 3 and 7) can be connected to asingle end of a primary side of a transformer to drive the transformerin a single ended manner. To implement a differential circuit, twoinstances of a driver circuit and a compensation circuit (such ascircuits 302, 304, 720, and 702 depicted in FIGS. 3 and 7) can beconnected, or a driver circuit and a compensation circuit can beconfigured to provide two differential outputs, to two ends of theprimary side of a transformer to drive the transformer in a differentialmanner.

FIG. 8 illustrates an example embodiment of a filter stage and a gainstage for the compensation circuit of FIG. 7. Referring to FIG. 8, thefilter stage 804 and gain stage 802 include differential inputs andoutputs, and can correspond to the filter circuit 722 and gain circuit724 of FIG. 7, respectively. In an example, the filter stage 804 caninclude operational amplifiers 810 and 812 coupled to respectivecapacitors 814 and 816. In an example, the gain stage can includeoperational amplifiers 806 and 808. Other implementations of the gainstage 802 and the filter stage 804 can also be used in differentembodiments.

FIG. 9A and FIG. 9B illustrate example embodiments of a compensationcircuit. Referring to FIG. 9A, the compensation circuit 900 includes afilter stage 916 and a driver stage 918. The filter stage 916 caninclude a transconductance stage 902 (with transconductance Gm1) coupledto a capacitor 904, forming a Gm-C filter. The driver stage 918 caninclude a transconductance stage 906 (with transconductance Gm2). Theoutput of the driver stage 918 can be coupled to an equivalent primarycircuit 908, which can include an inductance 910 and a resistance 912representing a termination impedance (e.g., termination impedance at asecondary side of a transformer, reflected back to the primary side ofthe transformer). The total output impedance can be designated as Zout914.

The compensation circuit 900 can be an example implementation of theclosed-loop compensation circuit 720 but with an open loop where theinput voltage node Vi and the output voltage node Vo are separated (in aclosed-loop operation, the input node Vi and the output node Vo are thesame).

The output current at the filtering stage 916 isI1=Vi*Gm1

The output current I1 is applied to the integrating capacitor C1,resulting in the voltage across C1 being given by

${V\; 1} = {\frac{I\; 1}{{sC}\; 1} = \frac{{Vi}*{Gm}\; 1}{{sC}\; 1}}$

Where

${w\; 1} = \frac{{Gm}\; 1}{C\; 1}$is the unity-gain frequency of the Gm-C integrator 902 and 904.

The output current at the driver stage 918 isIo=Gm2*V1

The output current Io is applied to the output impedance Zout, resultingin the voltage across Zout being given by

${{Vo} = {{{Io}*{Zout}} = {{{Gm}\; 2*V\; 1*{Zout}} = {{Vi}*{Gm}\; 1*{Gm}\; 2*\frac{Zout}{{sC}\; 1}}}}},$

where Zout is the parallel of the termination impedance and the opencircuit inductance (OCL) of the equivalent primary circuit 908.

${Zout} = \frac{sLoRo}{{Ro} + {sLo}}$

For low frequencies the term sLo<<Ro and the output impedance at lowfrequencies can be considered dominated by the inductor. The outputimpedance can be expressed as follows:Zout_((low freq)) ≅sLoTherefore, the gain of the loop of the compensation circuit 900 at lowfrequencies can be expressed as follows:

${Av} = {\frac{Vo}{Vi} = {{Gm}\; 1*{Gm}\; 2*\frac{Lo}{C\; 1}}}$

The input voltage (Vi) is amplified by the loop gain (Av) and isconverted into current (Io) by the transconductance factor (Gm2) of theintegrator 906 before being injected at the equivalent primary circuit908.

In an example, the compensation circuit 900 can operate in positivefeedback mode, and will be stable when |Av|<1. Additionally, differentC1 values can correspond to different equivalent inductance values for agiven |Av|. Different |Av| values can correspond to different currentgain slopes and may be used to select the baseline wander droop.Different |Av| values can also be used to limit the amount of injectedcurrent to minimize saturation effect in the transformer. Based on theabove equation for the loop gain, variations in inductance associatedwith the circuit 908 can be addressed by adjusting the capacitance C1 ofthe integrating capacitor 904 so as to keep the loop gain stable.

FIG. 9B illustrates the compensation circuit 900 in a closed-loopconfiguration, where the input voltage signal Vi is connected to theoutput voltage signal Vo using a connection 920. Additionally, a drivercircuit 922 is coupled to the output voltage signal Vo as well as theprimary equivalent circuit 908.

In an example, the compensation circuit can be integrated with atransformer (e.g., with the equivalent primary circuit 908), and thetransformer can include a temperature sensor. The temperature sensor canmonitor internal temperature of the transformer and transformerinductance (OCL) can be estimated based on the temperature (e.g., byusing a look-up table). In this regard, a gain (e.g., “Av”) correctioncan be made (e.g., by adjusting C1) when the transformer inductancechanges with temperature.

In an example, assuming transconductance of the compensation circuit 900is fixed, the medium frequency gain will be dominated by the value ofthe inductance Lo (of circuit 910) and the internal parameters Gm1, Gm2and capacitance (C1) of the integration capacitor 904. In this regard,individual transconductance values Gm1 and Gm2, inductance (Lo) andcapacitance (C1) can be controlled and adjusted dynamically to keep theloop gain (Av) constant. For any given value of external inductance(Lo), the loop transconductance (Gm1*Gm2) or the internal capacitance C1can be adjusted to ensure the stability of the loop gain target.

In an example, the inductance value (Lo) can be measured at start up ordynamically to adjust, for example, based on temperature and agingvariations. In another example, a transformer can be characterizedindividually in production tests and inductance values (OCL) can bestored in a look-up table. In this regard, for any given value of thetransformer OCL, the compensation loop can be adjusted to increase thelow frequency range of the transformer and minimize the voltage droop.

FIG. 10 illustrates a flow diagram of an example method for generating asignal to compensate baseline voltage wander, in accordance with anembodiment. Referring to FIG. 10, the example method 1000 may start at1010, when an input voltage signal is received from an input of anisolator circuit. For example and in reference to FIG. 7 and FIG. 9A,the primary equivalent circuit 706 can be used as an isolator circuit,and the compensation circuit 720 can receive an input voltage signal Vi.

At 1020, the received input voltage signal can be filtered to generate afiltered representation of the voltage signal. For example, the inputsignal Vi can be filtered by the filtering circuit (722 or 916) togenerate the filtered representation V1 of the input voltage signal Vi.At 1030, a current ramp signal is generated, where the ramp signal isproportional to inductance associated with the isolator circuit and avoltage magnitude extracted from the filtered representation of thevoltage signal. For example, the driver stage (726 or 918) can generatethe current ramp signal Io, which can be proportional to magnitude ofthe input voltage and inductance of the isolator circuit (706 or 908).At 1040, the current ramp signal is injected into the input of theisolator to reduce or suppress voltage droop in the input voltage signalwhen the input voltage signal is applied to the input of the isolator.For example, the generated output current ramp signal I0 can be injectedinto the isolator circuit (706 or 908) to suppress voltage droop.

Even though baseline wander correction, as described herein, isperformed with regards to a primary side of an isolation circuit (e.g.,a transformer), the disclosure is not limited in this regard. Since atransformer includes a primary and a secondary side that are coupled,correcting the voltage droop in the primary side will automaticallycorrect the droop in the secondary side as well. Put another way,although the current compensation is physically performed in the primaryside (as explained herein), baseline wander correction takes place inboth the primary and the secondary sides of the isolation circuit.

Various Notes & Examples

Example 1 is a circuit for compensation of baseline voltage wander at aninput of an isolator, the circuit comprising: a filter circuit, whereinthe filter circuit is configured to receive an input voltage signal froman input of the isolator and configured to generate a filteredrepresentation of the voltage signal; and a driver circuit configured touse information about a voltage magnitude extracted from the filteredrepresentation of the voltage signal to generate an output current rampsignal, the driver circuit configured to inject the output current rampsignal into the input of the isolator to reduce or suppress voltagedroop in the input voltage signal when the input voltage signal isapplied to the input of the isolator.

In Example 2, the subject matter of Example 1 optionally includes a gaincircuit configured to amplify the filtered representation of the voltagesignal, and provide the amplified filtered representation of the voltagesignal to the driver circuit for generating the output current rampsignal.

In Example 3, the subject matter of any one or more of Examples 1-2optionally includes wherein the isolator comprises an inductive device.

In Example 4, the subject matter of Example 3 optionally includeswherein the inductive device has inductance of less than 80 microHenry.

In Example 5, the subject matter of any one or more of Examples 3-4optionally includes wherein the driver circuit is configured to generatethe output current ramp signal at least in part using information aboutthe voltage magnitude extracted from the filtered representation of thevoltage signal and a value of an inductance corresponding to theinductive device.

In Example 6, the subject matter of Example 5 optionally includeswherein the driver circuit is configured to generate the output currentramp signal having a slope generated using information about a value ofthe voltage magnitude extracted from the filtered representation of thevoltage signal and the value of the inductance corresponding to theinductive device.

In Example 7, the subject matter of any one or more of Examples 1-6optionally includes wherein the isolator comprises a transformer.

In Example 8, the subject matter of any one or more of Examples 1-7optionally includes wherein the driver circuit is configured toestablish a zero-average DC current for the output current ramp signal.

In Example 9, the subject matter of Example 8 optionally includeswherein the driver circuit and filter circuit are configured to reducethe voltage droop to maintain the input voltage signal within aspecified range of a desired input voltage signal while maintaining azero-average DC current for the output current signal.

In Example 10, the subject matter of any one or more of Examples 1-9optionally includes wherein the driver circuit is configured to generatethe output current ramp signal including a ramp duration correspondingto a transmit pulse duration, the transmit pulse included as a portionof the input voltage signal.

In Example 11, the subject matter of any one or more of Examples 1-10optionally includes wherein the driver circuit is configured to generatethe output current ramp signal including releasing the ramp signal inresponse to information about one or more of a transmit pulse durationor a current limit established to avoid saturation of the isolator.

In Example 12, the subject matter of any one or more of Examples 1-11optionally include wherein the filter circuit and the current drivercircuit are coupled in a closed-loop configuration, with an output ofthe current driver circuit coupled to an input of the filter circuit.

In Example 13, the subject matter of any one or more of Examples 1-12optionally include wherein the filtering circuit comprises atransconductance amplifier coupled to a capacitor.

Example 14 is a compensation loop circuit for compensation of baselinevoltage wander at an input of an isolator, the circuit comprising: afilter circuit coupled to an input of the isolator, the filter circuitconfigured to receive an input voltage signal from the input of theisolator and generate a filtered representation of the voltage signal; again circuit coupled to an output of the filter circuit, the gaincircuit configured to amplify the filtered representation of the voltagesignal to generate an amplified voltage signal; and a driver circuitcoupled to an output of the gain circuit and an input of the filtercircuit to form the compensation loop circuit, the driver circuitconfigured to generate an output current ramp signal based on theamplified voltage signal, wherein the driver circuit is furtherconfigured to inject the output current ramp signal into the input ofthe isolator to reduce or suppress voltage droop in the input voltagesignal when the input voltage signal is applied to the input of theisolator, and wherein the output current ramp signal is configurablebased on a voltage gain associated with the input voltage signal and anoutput voltage signal corresponding to the output current ramp signal.

In Example 15, the subject matter of Example 14 optionally includeswherein the filter circuit comprises an integrating capacitor, andwherein the voltage gain of the compensation loop circuit is configuredbased on adjusting capacitance of the integrating capacitor, to changethe output current ramp signal.

Example 16 is a method for generating a signal to compensate baselinevoltage wander, the method comprising: receiving an input voltage signalfrom an input of an isolator circuit; filtering the received inputvoltage signal to generate a filtered representation of the voltagesignal; generating a current ramp signal proportional to inductanceassociated with the isolator circuit and a voltage magnitude extractedfrom the filtered representation of the voltage signal; and injectingthe current ramp signal into the input of the isolator to reduce orsuppress voltage droop in the input voltage signal when the inputvoltage signal is applied to the input of the isolator.

In Example 17, the subject matter of Example 16 optionally includesamplifying the filtered representation of the voltage signal to generatean amplified voltage signal; and converting the amplified voltage signalinto a current signal to generate the current ramp signal, wherein thecurrent ramp signal is configurable based on a voltage gain associatedwith the input voltage signal and an output voltage signal correspondingto the current ramp signal.

In Example 18, the subject matter of Example 17 optionally includesselecting a desired voltage gain based on one or both of the inductanceor temperature of the isolation circuit.

In Example 19, the subject matter of Example 18 optionally includesadjusting the voltage gain based on the desired voltage gain, to modifythe current ramp signal.

In Example 20, the subject matter of Example 19 optionally includeswherein adjusting the voltage gain further comprises: adjusting one orboth of transconductance or capacitance of at least one circuit used togenerate the currant ramp signal.

Each of the non-limiting examples described herein can stand on its own,or can be combined in various permutations or combinations with one ormore of the other examples.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

In the event of inconsistent usages between this document and anydocuments so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of“at least one” or “one or more.” In this document,the term “or” is used to refer to a nonexclusive or, such that “A or B”includes “A but not B,” “B but not A,” and “A and B,” unless otherwiseindicated. In this document, the terms “including” and “in which” areused as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that suchembodiments can be combined with each other in various combinations orpermutations. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A circuit for compensation of baseline voltagewander at an input of an isolator, the circuit comprising: a filtercircuit, wherein the filter circuit is configured to receive an inputvoltage signal and generate a filtered representation of the inputvoltage signal; and a driver circuit configured to use information abouta voltage magnitude extracted from the filtered representation of theinput voltage signal to generate an output current ramp signal, and thedriver circuit is further configured to inject the output current rampsignal into the input of the isolator to reduce or suppress voltagedroop in the input voltage signal, wherein the input voltage signal andthe output current ramp signal are both applied to the input of theisolator.
 2. The circuit of claim 1, further comprising: a gain circuitconfigured to amplify the filtered representation of the input voltagesignal, and provide the amplified filtered representation of the inputvoltage signal to the driver circuit for generating the output currentramp signal.
 3. The circuit of claim 1, wherein the isolator comprisesan inductive device.
 4. The circuit of claim 3, wherein the inductivedevice has inductance of less than 80 microHenry.
 5. The circuit ofclaim 3, wherein the driver circuit is configured to generate the outputcurrent ramp signal at least in part using information about the voltagemagnitude extracted from the filtered representation of the inputvoltage signal and a value of an inductance corresponding to theinductive device.
 6. The circuit of claim 5, wherein the driver circuitis configured to generate the output current ramp signal having a slopegenerated using information about a value of the voltage magnitudeextracted from the filtered representation of the input voltage signaland the value of the inductance corresponding to the inductive device.7. The circuit of claim 1, wherein the isolator comprises a transformer.8. The circuit of claim 1, wherein the driver circuit is configured toestablish a zero-average DC current for the output current ramp signal.9. The circuit of claim 8, wherein the driver circuit and filter circuitare configured to reduce the voltage droop to maintain the input voltagesignal within a specified range of a desired input voltage signal whilemaintaining a zero-average DC current for the output current signal. 10.The circuit of claim 1, wherein the driver circuit is configured togenerate the output current ramp signal including a ramp durationcorresponding to a transmit pulse duration, the transmit pulse includedas a portion of the input voltage signal.
 11. The circuit of claim 1,wherein the driver circuit is configured to generate the output currentramp signal including releasing the ramp signal in response toinformation about one or more of a transmit pulse duration or a currentlimit established to avoid saturation of the isolator.
 12. The circuitaccording to claim 1, wherein the filter circuit and the driver circuitare coupled in a closed-loop configuration, with an output of the drivercircuit coupled to an input of the filter circuit.
 13. The circuitaccording to claim 1, wherein the filter circuit comprises atransconductance amplifier coupled to a capacitor.
 14. A compensationloop circuit for compensation of baseline voltage wander at an input ofan isolator, the circuit comprising: a filter circuit coupled to aninput of the isolator, the filter circuit configured to receive an inputvoltage signal from the input of the isolator and generate a filteredrepresentation of the voltage signal; a gain circuit coupled to anoutput of the filter circuit, the gain circuit configured to amplify thefiltered representation of the voltage signal to generate an amplifiedvoltage signal; and a driver circuit coupled to an output of the gaincircuit and an input of the filter circuit to form the compensation loopcircuit, the driver circuit configured to generate an output currentramp signal based on the amplified voltage signal, wherein the drivercircuit is further configured to inject the output current ramp signalinto the input of the isolator to reduce or suppress voltage droop inthe input voltage signal, wherein the input voltage signal and theoutput current ramp signal are both applied to the input of theisolator, and wherein the output current ramp signal is configurablebased on a voltage gain associated with the input voltage signal and anoutput voltage signal corresponding to the output current ramp signal.15. The compensation loop circuit of claim 14, wherein the filtercircuit comprises an integrating capacitor, and wherein the voltage gainof the compensation loop circuit is configured based on adjustingcapacitance of the integrating capacitor, to change the output currentramp signal.
 16. A method for generating a signal to compensate baselinevoltage wander, the method comprising: receiving an input voltage signalfrom an input of an isolator circuit; filtering the received inputvoltage signal to generate a filtered representation of the inputvoltage signal; generating a current ramp signal proportional toinductance associated with the isolator circuit and a voltage magnitudeextracted from the filtered representation of the input voltage signal;and injecting the current ramp signal into the input of the isolator toreduce or suppress voltage droop in the input voltage signal, whereinthe input voltage signal and the current ramp signal are both applied tothe input of the isolator.
 17. The method according to claim 16, furthercomprising: amplifying the filtered representation of the voltage signalto generate an amplified voltage signal; and converting the amplifiedvoltage signal into a current signal to generate the current rampsignal, wherein the current ramp signal is configurable based on avoltage gain associated with the input voltage signal and an outputvoltage signal corresponding to the current ramp signal.
 18. The methodaccording to claim 17, further comprising: selecting a desired voltagegain based on one or both of the inductance or temperature of theisolation circuit.
 19. The method according to claim 18, furthercomprising: adjusting the voltage gain based on the desired voltagegain, to modify the current ramp signal.
 20. The method according toclaim 19, wherein adjusting the voltage gain further comprises:adjusting one or both of transconductance or capacitance of at least onecircuit used to generate the current ramp signal.